Genetic Potential and Limitations of Ethiopian Chickpea (Cicer Arietinum L.) Germplasm for Improving Attributes of Symbiotic Nitrogen Fixation, Phosphorus Upatke and Use Efficiency, and Adzuki Bean Beetle (Callosobruchus Chinensis L.) Resistance
No Thumbnail Available
Date
2012-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Chickpea (Cicer arietinum L.) is one of the most important food legumes
grown all over the world. In Ethiopia, chickpea is among the most important
food legumes both in terms of area coverage and volume of production. The
production of chickpea is important not only in terms of human and animal
nutrition but also in terms of ecological sustainability through symbiotic
nitrogen fixation. Despite the importance, productivity of chickpea is
constrained at least in part by production problems related to the inherent
low-yielding potential of the local cultivars, production without application
of adequate inputs including fertilizers and post-harvest insect pest damage
particularly adzuki bean beetle (Callosobruchus chinensis L.).
Ethiopia is known as one of the centers of secondary diversity for
chickpea. Genetic resources with proven performance for better symbiotic
nitrogen fixation, phosphorus uptake and use efficiency and adzuki bean
beetle resistance are limited for focused utilization in chickpea breeding
programs. Characterization and evaluation of genetic make-up of the
Ethiopian chickpea germplasm accessions is, therefore, essential to designing
effective breeding programs.
Genetic diversity and population structure of 155 chickpea genotypes
were studied using 33 microsatellite (SSR) markers. A series of field and
laboratory experiments were also undertaken in 2009-2010 in Ethiopia to
characterize and evaluate Ethiopian chickpea germplasm for attributes of
symbiotic nitrogen fixation, phosphorus use efficiency and adzuki bean
beetle resistance. The field studies for symbiotic nitrogen fixation and
phosphorus use efficiency were undertaken at Ambo and Ginchi while the
adzuki bean beetle resistance study was conducted in entomology
laboratories at Debre Zeit, Holetta and Ambo in Ethiopia. The tests for
symbiotic nitrogen fixation and phosphorus uptake and use efficiency were
conducted with 155 genotypes and 130 genotypes were tested for adzuki
bean beetles resistance. Randomized complete block designs with 4
replications for symbiotic nitrogen fixation, 2 for phosphorus uptake and use
efficiency and 3 for resistance to adzuki bean beetle were used. The
difference technique, with a non-nodulating reference genotype was
employed to estimate nitrogen fixation and the balance method was used to
estimate phosphorus uptake and use efficiency.
Molecular analysis of variance showed variation of 73% within and 27%
between populations. Introduced genotypes had higher polymorphism
(70.27%) than the local accessions (36-57%). Collections from Shewa,
Harargie, W. Gojam and S. Gonder regions showed the second higher
polymorphism (50-57%) than the rest of the local accessions (36-45%).
Accessions from adjoining eco-geographical origins mostly showed
tendencies for more genetic similarity than those from far isolated origins.
Cluster analyses at the molecular level grouped the genotypes into five
clusters. The first cluster (C1) constituted accessions from Arsi, the second (C2)
from Gojam and Gonder, the third (C3) from Harargie and E. and N. Shewa,
the fourth (C4) from W. Shewa, Tigray and Wello regions and the fifth (C5) all
improved genotypes. Improved Kabuli and Desi types fell into a distinct
cluster (C5) regardless of the difference in seed types. Analysis of variance of symbio-agronomic characters, phosphorus
uptake and use efficiency and adzuki bean beetle resistance showed
significant differences among the genotypes, locations and genotype by
location interaction effects for a number of traits. Genotype by phosphorus
level interaction effects were non-significant except in a few cases.
A number of landraces superior to introduced genotypes were identified
for attributes of symbio-agronomic characters except for seed size where the
best genotypes were all from exotic sources. The amount of fixed nitrogen
ranged from 13-49% in foliage, 30-44% in grain and 28-40% in total above
ground biomass. Grain yield performance varied from 31-70 g 5 plants-1 and
seed size from 82-288 g/1000 seeds. The top 5% best accessions for total
(shoot + grain) nitrogen fixation include Acc. Nos. 41222, 41029, 41021,
41074, 41075, 41129, 41320 and 41026. There were also some other
genotypes which had better fixations either in their shoots (e.g. 41103) or
grains (e.g. 207734). Two introductions from ICRISAT, namely ICC 5003 and
ICC 4973, were also among the top 5% best fixers of nitrogen in their shoot.
The best assimilators of fixed nitrogen were Acc. Nos. 41115, 207659,
219799, 207150, 41277, 41113 and 207894.
The application of phosphorus fertilizer increased a number of
characters including symbiotic nitrogen fixation. Yield increments of 15% at
Ambo and 17% at Ginchi were recorded due to application of phosphorus.
The top 5% best efficient, responder genotypes for grain yield include Acc.
No. 41274, 41111, 207742, 207563, 207763, 231328, ICC 19180 and
41114. Three of these accessions, namely 41274, 207563 and 41111, also
repeated best performances as efficient, responder genotypes for biomass
weight. Other efficient, responder genotypes for biomass weight include: Acc.
Nos. 207743, 41015, 41066, 41185 and Ejere.
Complete resistance to adzuki bean beetle was not observed among the
genotypes but Acc. Nos. 41320, 41289, 41291, 41134, 41315, 207658,
41103, 41168, 41142, 41174, 41029, 41207, 209087, 231327, 41161 and
41008 showed partial resistance. Significant progresses were achieved in
grain yield and seed size from past breeding efforts but the same efforts had
inadvertently increased seed susceptibility to adzuki bean beetle.
Cluster analysis grouped the genotypes into six cluster for symbioagronomic
characters, five clusters in the absence and six clusters in the
presence of phosphorus, respectively, for attributes of phosphorus uptake
and use efficiency and three clusters for attributes of adzuki bean beetle
resistance. The higher number of clusters when the crop was grown with
phosphorus may be a manifestation of more genetic diversity due to the
application of phosphorus. The limited genetic diversity for response
characters to infestation by adzuki bean beetle may imply the need for
characterization of additional landraces and exotic genotypes.
The Mahalanobis’s D2 statistics mostly showed significant genetic
distances between clusters constituted local landraces on the one hand and
introduced genotypes on the other. This indicated that there were distinct
multivariate differences between landraces and introduced genotypes. No clear
interrelationship was observed between the origins of the landraces within Ethiopia and the pattern of genetic diversity. Different characters had different
contribution to the total differentiation of the populations in all the cases.
The study on symbio-agronomic traits showed significant positive
correlations between a number of characters. Grain yield was positively
associated with fixed nitrogen assimilation efficiency, shoot, grain, and
above ground biomass nitrogen yields and nitrogen harvest index.
Agronomic characters like grain filling period, pod and seed numbers, shoot,
and total above ground biomass accumulation, harvest index, grain
production efficiency and biomass production and economic growth rates
also positively correlated with grain yield. Increased nitrogen yield, nitrogen
harvest index, fixed nitrogen assimilation efficiency and above ground
biomass may be more important than the per se concentration of nitrogen in
plant tissue. Characters like shoot, grain and total biomass nitrogen
contents and fixation, fixed nitrogen assimilation efficiency, seed size, grain
filling period showed higher genetic variation, broad-sense heritability and
expected genetic gains from selection.
The study on phosphorus uptake and use efficiency revealed significant
positive correlations within plant tissue (shoot, seed and biomass) phosphorus
contents (r = 0.22-0.85), between plant tissue phosphorus contents and
phosphorus yields (r = 0.22-0.99), within plant tissue phosphorus yields (r =
0.23-0.89) and within parameters of phosphorus uptake and use efficiency in
a number cases. Grain yield and economic growth and biomass production
rates, grain production efficiency, and shoot and biomass dry weight showed
significant positive correlations (r = 0.70-0.99) with phosphorus yield
efficiency. Broad sense heritability values ranged from 60-93% and genetic
advance values ranged from 4-62% in the absence of phosphorus. The
corresponding broad sense heritability and genetic advance values in the
presence of phosphorus ranged from 59-93% and 4-79% in that order.
In the study of bruchid resistance seed-related traits (seed size, percent
seed coat weight and seed weight loss) exhibited larger heritable variation
than insect-related traits (number of eggs and adults, days to adult
emergence, number of uninfected seed and adult recovery). Broad-sense
heritability for seed and insect-related traits varied from 43-76% and 0.20-
11%, respectively. The corresponding expected genetic gains from selection as
percent of mean ranged from 28-42% and 0.01-6% in the same order.
Significant positive correlations were found among seed weight loss and three
component characters, i.e. number of eggs and adults emerged and seed size.
The results from these series of studies suggests possibilities for
identification of chickpea genotypes superior for symbio-agronomic
characters, phosphorus uptake and use efficiency and adzuki bean beetle
resistance to the varieties released so far, indicating the need for the
initiation of a planned breeding program. Further implications of the
findings as regard germplasm collection, conservation and eco-geographical
pattern evolution are also discussed.
Description
Keywords
Biology